Method for reuse of wafers for growth of vertically-aligned wire arrays

ABSTRACT

Reusing a Si wafer for the formation of wire arrays by transferring the wire arrays to a polymer matrix, reusing a patterned oxide for several array growths, and finally polishing and reoxidizing the wafer surface and reapplying the patterned oxide.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 12/176,100, filed Jul. 18, 2008 (now U.S. Pat. No. 7,910,461),which application is related to an claims the benefit of the followingcopending and commonly assigned U.S. patent applications: U.S. PatentApplication No. 61/127,437, titled “Regrowth of Silicon Rod Arrays,”filed on May 13, 2008; and U.S. Patent Application No. 60/966,432,titled “Polymer-embedded Semiconductor Rad Arrays,” filed on Aug. 28,2007; the entire contents of these applications are incorporated hereinby reference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

The U.S. Government has certain rights in this invention pursuant toGrant No. DE-FG02-03ER15483 awarded by DOE.

BACKGROUND

1. Field

This disclosure relates to fabrication of semiconductor structures onsubstrates. More specifically, the present disclosure describes methodsfor growing semiconductor structures on substrates and reusing thesubstrates.

2. Description of Related Art

The following commonly assigned and copending applications describe thegrowth of vertically aligned Si wire arrays on a substrate: “U.S. PatentApplication No. 60/961,170, titled “Fabrication of Wire Array Samplesand Controls,” filed on Jul. 19, 2007; U.S. Patent Application No.60/961,169, titled “Growth of Vertically Aligned Si Wire Arrays OverLarge Areas (>1 cm²) with Au and Cu Catalysts,” filed on Jul. 19, 2007.These methods to grow high quality, vertically aligned arrays of Siwires may require an expensive, single crystal Si (111) wafer to be usedas a substrate. This may hinder the potential of these wire arrays to beused as part of a cheaper alternative to traditional, planar junctionsolar cells.

SUMMARY

The following copending and commonly assigned patent applicationdescribes methods for encapsulating semiconductor structures grown on asubstrate within a binder material layer: U.S. Patent Application No.60/966,432, titled “Polymer-embedded Semiconductor Rod Arrays,” filed onAug. 28, 2007. Embodiments of the present invention allow for theseparation of semiconductor structures embedded in the binder materiallayer from the substrate and then reuse of the substrate for growth ofadditional semiconductor structures. Through the reuse of the substrate,the expense of the wafer can be reduced within the overall process.

One embodiment of the present invention is a method for fabricatingsemiconductor structures comprising the steps of: (a) fabricatingsemiconductor structures on a substrate; (b) encapsulating thefabricated semiconductor structures in a binder material matrix; (c)releasing the fabricated semiconductor structures from the substrate;and (d) reusing the substrate for fabricating additional semiconductorstructures by repeating steps (a) through (c).

Another embodiment of the present invention is a method for fabricatingset of Si wire arrays comprising the following steps: growing Si wirearrays on a single crystal Si wafer using a patterned oxide layerdeposited on the Si wafer; transferring the grown Si wire arrays to abinder material matrix; removing binder material residue and wire arrayremnants from the Si wafer; and reusing the Si wafer for fabricatingadditional Si wire arrays by repeating the steps of growing Si wirearrays, transferring the grown Si wire arrays to a binder materialmatrix, and removing binder material residue and wire array remnants.

Another embodiment of the present invention is a method for reusing asubstrate for semiconductor structure fabrication comprising: growingsemiconductor structures on a substrate using a patterned oxide layerdeposited on the substrate, wherein the patterned oxide layer acceptsthe deposition of catalyst metal into openings in the patterned oxidelayer to support growth of the semiconductor structures; transferringthe grown semiconductor structures to a binder material matrix; removingbinder material residue and semiconductor structure remnants from thesubstrate; and reusing the substrate for fabricating additionalsemiconductor structures by repeating the steps of growing semiconductorstructures; transferring the grown semiconductor structures to a bindermaterial matrix, and removing binder material residue and semiconductorstructure remnants.

No limitation is intended by the description of exemplary embodimentsbriefly described above or those described in additional detail below.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIGS. 1A-1G illustrate steps for growing vertically aligned Si wirearrays on a Si substrate.

FIGS. 2A-2C illustrate steps for embedding and removing semiconductorstructures from a substrate.

FIGS. 3A-3C illustrate steps for embedding and removing semiconductorstructures from a substrate when the semiconductor structures are notcompletely encapsulated.

FIGS. 4A-4F are SEM images showing the results of various steps of amethod for reusing a substrate for semiconductor structure growth.

FIGS. 5A-5D are SEM images of wire arrays achieved through fourgenerations of a method for reusing a Si wafer for wire array growth.

FIG. 6 shows a tilted view SEM image of a Si wire array grown from aSi(111) wafer that has been mechanically polished and then thermallyoxidized.

DETAILED DESCRIPTION

Within this description, the terms “wires,” “rods,” “whiskers,” and“pillars” and other similar terms may be used synonymously, except asotherwise indicated. Generally, these terms refer to elongate structureswhich have lengths and widths, where the length is defined by thelongest axis of the structure and the width is defined by the axisgenerally normal to the longest axis of the structure. The term ‘aspectratio’ refers to the ratio of a structure's length to its width. Hence,the aspect ratios of the elongate structures will greater than one. Theterms “ball,” “spheroid,” “blob” and other similar terms may also beused synonymously, except as otherwise indicated. Generally, these termsrefer to structures with the width defined by the longest axis of thestructure and the length defined by the axis generally normal to thewidth. Hence, the aspect ratio of such structures will generally beunity or less than unity. Further the term “vertical” with reference towires, rods, whiskers, pillars, etc., generally refers to structuresthat have a length direction that is elevated somewhat from horizontal.The term “vertical alignment” generally refers to an alignment ororientation of a structure or structures that is elevated fromhorizontal. The structure or structures do not have to be completelynormal to horizontal to be considered to have a vertical alignment. Theterm “array” generally refers to multiple numbers of structuresdistributed within an area and spaced apart, unless otherwise indicated.Structures within an array all do not have to have the same orientation.The terms “vertically aligned array” or “vertically oriented array”generally refer to arrays of structures where the structures haveorientations elevated from a horizontal orientation up to orientationscompletely normal to a horizontal orientation, but the structures withinthe array may or may not have all the same orientations with respect tohorizontal. The term “ordered” generally refers to the placement ofelements in a specified or predetermined pattern where the elements havedistinct spatial relationships to one another. Hence, the term “orderedarray” generally refers to structures distributed within an area withdistinct, specified or predetermined spatial relationships to oneanother. For example, the spatial relationships within an ordered arraymay be such that the structures are spaced apart from one another bygenerally equal distances. Other ordered arrays may use varying, butspecified or predetermined, spacings.

Within this description, the term “semiconductor” is generally used torefer to elements, structures, or devices, etc. comprising materialsthat have semiconductive properties, unless otherwise indicated. Suchmaterials include, but are not limited to: elements from Group IV of theperiodic table: materials including elements from Group IV of the periodtable; materials including elements from Group III and Group V of theperiodic table; materials including elements from Group II and Group VIof the periodic table; materials including elements from Group I andGroup VII of the periodic table; materials including elements from GroupIV and Group VI of the periodic table; materials including elements fromGroup V and Group VI of the periodic table; and materials includingelements from Group II and Group V of the periodic table. Othermaterials with semiconductive properties may include: layeredsemiconductors; metallic alloys; miscellaneous oxides; some organicmaterials, and some magnetic materials. The term “semiconductorstructure” refers to a structure consisting of, at least in part,semiconductor material. A semiconductor structure may comprise eitherdoped or undoped material.

As indicated, methods to fabricate semiconductor structures on asubstrate may require an expensive, single crystal Si (111) wafer beused as the substrate. This hinders the potential of these structures tobe used as part of cheaper alternatives for complex semiconductordevices, such as solar cells to be used in place of traditional planarjunction solar cells. However, by separating the substrate from thesemiconductor structures and reusing it for subsequent semiconductorstructure fabrication, the expense of the wafer can be reduced withinthe overall process. The present disclosure describes the fabrication ofmultiple, high quality semiconductor structures from a given Si (111)wafer. As an example, fabrication of vertically-aligned Si wire arraysfrom a Si wafer substrate is described. Before removing it from thesubstrate, the wire array is embedded in polymer to maintain itsvertically aligned structure. An oxide template used to control the wiredimensions is then recovered by a selective etching step, and metalcatalyst is electrodeposited back into the template holes to enable thegrowth of a new wire array. After several repetitions of this procedure,a new template may be formed by polishing and thermal oxidation so thatthe cycle can continue.

Embodiments of the present invention may use various methods forfabrication of semiconductor structures. Discussed immediately below isthe fabrication of semiconductor structures using V-L-S growthtechniques. However, the semiconductor structures may be deposited onthe substrate, an example of which is presented below. The semiconductorstructures may also be etched from the substrate, an example of which isalso presented below. Embodiments of the present invention where thesemiconductor structures are fabricated from etching the substrateprovide for less opportunity to reuse the substrate, since the substrateis, to some extent, used up during the fabrication and reuse process.However, such top-down fabrication techniques are within the scope ofembodiments of the present invention.

FIGS. 1A-1G illustrate a process for growing semiconductor structuresusing a vapor-liquid-solid (VLS) growth process. FIGS. 1A-1Gspecifically illustrate the growth of Si wire arrays. Other techniquesfor growing the semiconductor structures may also be used in accordancewith embodiments of the present invention. Therefore, embodiments of thepresent invention are not limited to the semiconductor structurefabrication techniques disclosed or described herein.

An Si <111> wafer may be used as the material from which thesemiconductor structures are grown. All or portions of the wafer may bedoped. For example, a degenerately doped N-type Si wafer may be used. Asshown in FIG. 1A, a surface oxide layer 20 is thermally grown on thewafer 10. The surface oxide layer may be grown to a thickness of 285 nm,300 nm, or other thicknesses. The oxide layer 20 may also be depositedvia chemical vapor deposition (CVD) or other methods known in the art.

As shown in FIG. 1B, a photoresist layer 30 is applied. The photoresistlayer may comprise S1813 photoresist from MicroChem Corp. (Newton,Mass., USA) or other photoresist material. The photoresist layer 30 isthen exposed to a desired array pattern and developed with a developerto form a desired pattern of holes 35 in the resist layer 30 as shown inFIG. 1C. The developer may comprise MF-319 or other developers known inthe art. The patterned resist layer 30 is then used to etch the oxidelayer 20 on the Si wafer 10 as shown in FIG. 1D. Etching of the oxidelayer may be achieved by using hydrofluoric acid compositions such asbuffered HF (9% HF, 32% NH₄F) from Transene Company, Inc. (Danvers,Mass., USA). Other etching techniques known in the art may also be usedto etch the oxide layer 20. The result of the etching will be a patternof holes 37 in the oxide layer as shown in FIG. 1D.

A growth catalyst 50 is then thermally evaporated onto the resist layer30 and into the holes 37 in the oxide layer 20 as shown in FIG. 1E. Forexample, 500 nm of gold may be thermally evaporated onto the resistlayer 30 and into the holes 37. Other catalysts, such as, but notlimited to, Cu, Pt or Ni, may also be used. Lift-off of the photoresistlayer 30 is then performed, leaving catalyst islands 57 separated by theoxide in the oxide layer 20 as shown in FIG. 1F.

The wafer 10 with the patterned oxide layer 20 and the depositedcatalyst may then be annealed. Preferably, the annealing is performed ina tube furnace at a temperature between 900 to 1000° C. or at atemperature of about 1050° C. for 20 minutes with the application of 1atm of H₂ at a flow rate of 1000 sccm (where SCCM denotes cubiccentimeters per minute at STP). Growth of wires on the wafer 10 is thenperformed. FIG. 1G shows the growth of wires 40 in a wire array throughthe application of a growth gas. Preferably, the wires 40 are grown in amixture of H₂ (1000 sccm) and SiCl₄ (20 sccm) at about 1 atm. The wires40 may be grown for between 20 to 30 minutes at temperatures between850° C. to 1100° C. or with different growth times, pressures, and orflow rates.

After the fabrication of the semiconductor structures, binder materialis applied to encapsulate the semiconductor structures grown on thesubstrate and then the removal of the encapsulated structures embeddedin the binder material layer. FIGS. 2A-2C illustrate the application andremoval process. FIG. 2A shows a substrate 200 with an oxide layer 205above the substrate and with semiconductor rod arrays 210 projectingfrom the substrate 200 and an oxide layer 205. FIG. 2B shows theapplication of a binder material 220 to the substrate 200 and oxidelayer 205 and around the semiconductor rod arrays 210. FIG. 2C shows thestructure obtained when the binder material 220 with the embedded rodarrays 210 are removed from the substrate 200 and oxide layer 205. Asindicated above, semiconductor structures other than semiconductor rodarrays may be embedded within a binder material layer. Note also thatthe substrate 200 and the oxide layer 205 may each comprise one or morelayers.

The binder material may comprise polydimethylsiloxane (PDMS) polymer.The polydimethylsiloxane polymer base may comprise Sylgard 184 PDMS fromDow Corning or other such materials. The polymer base and curing agentare mixed in a 10:1 w/w ratio and stirred. The uncured polymer isdiluted with methylene chloride (1.0 g/2.0 mL) and drop-cast on thesemiconductor rod arrays such that a smooth polymer surface ispreferably observed. These arrays are then allowed to sit for some timeto allow slow evaporation of the methylene chloride. After 13-16 hoursthe PDMS is still tacky, and is cured by heating to 120° C. for 1.5-2.0hours. After cooling, the PDMS overlayer and embedded rods are removedfrom the substrate and oxide layer using a cutting device, such asscraping the oxide layer with a razor blade. The resulting polymer filmhas the semiconductor rod arrays embedded with the same ordering asobserved on the substrate.

The method described above may provide for electrical contact to thebottom ends of the semiconductor rod arrays (the ends which werepreviously connected to the substrate), but the top ends of the rodarrays may be covered by the polymer, making electrical contact to thoseends more difficult. In an alternative method of binder materialapplication, a thinner binder material layer is applied to the substrateand around the semiconductor rod arrays. FIGS. 3A-3C illustrate thismethod of application.

FIG. 3A shows a substrate 200 with an oxide layer 205 above thesubstrate 205 and with semiconductor rod arrays 210 projecting from thesubstrate 200 and oxide layer 205. FIG. 3B shows the application of abinder material layer 225 to a top surface of the oxide layer 205 abovesubstrate 200 and around the semiconductor rod arrays 210, but at athickness less than the height of the rod arrays. FIG. 3C shows thestructure obtained when the binder material 225 with the embedded rodarrays 210 projecting from the binder material 225 are removed from thesubstrate 200 and oxide layer 205.

In the alternative method described above, spin casting may be used toapply the binder material. For example, the polymer base and curingagent mix described above may be diluted with a solution ofhexamethylcyclotrisiloxane (Alfa Aesar, 97%, nearly saturated inmethylene chloride), where the preferred dilution ratio may be fourparts hexamethylcyclotrisiloxane to one part of the polymer and curingagent mix. To produce a thinner film, the low-boiling-point siloxane wasadded to the PDMS solution that is used to form the polymer/rod arraycomposite. The diluted mixture is then spin-cast on the rod arrays at1000 rpm for 2 min. After spin-coating, the methylene chloride rapidlyevaporates, and the samples are cured at 150° C. for 0.5 hours. Thelow-boiling-point siloxane evaporated significantly during the curingstep, resulting in 20 μm thick polymer films in which greater than 50%of the wires were exposed. After curing and cooling, the PDMS overlayerand embedded rods are again removed from the substrate and oxide layerusing a cutting device.

FIG. 4A is a SEM image of a wire array grown on a substrate using themethods described above, where the majority of the image is a top-downview of the wire array with a 10 μm scale and the inset is a 70° tiltedview of the wire array with a 20 μm scale. FIG. 4B is a top down SEMimage (with the same scale as FIG. 4A) of a removed binder materiallayer with embedded rod arrays (the inset in FIG. 4B shows a 70° tiltedimage). FIG. 4C is a top-down SEM image (with the same scale as FIG. 4A)of the substrate surface left behind after the removal of the bindermaterial layer (the inset in FIG. 4C shows a 70° tilted image). Inparticular, FIG. 4C shows the wire stubs and polymer residue left afterthe removal of the binder material layer and the embedded wire arrays.

Reuse of the substrate for subsequent semiconductor growth may beinitiated by etching the substrate after the removal of the bindermaterial layer to remove any semiconductor structure remnants andpolymer residue. For example, if a Si wafer has been used for the growthof Si wire arrays, a KOH etch may be used to prime wafer surface forwire growth. The etching may be achieved by immersing the wafers for 90seconds in a 4.5 M KOH (aq) etchant maintained at 80° C. under stirring.Preferably, the wafer is examined using an optical microscope to ensurethat the polymer residue and wire stubs have been fully removed. FIG. 4Dshows a top-down SEM image of a wafer after a KOH etch (the inset inFIG. 4D shows a 70° tilted image). If necessary, the wafer may bereimmersed in the etchant until no residue or wire stubs remain.Experimentation indicates that the wafer surface can be cleaned byimmersion in the etchant for 120 seconds or less. Etching in this mannershould leave in place the patterned oxide layer that will be used as atemplate for subsequent array growth.

Alternative embodiments of the present invention may not have a step forthe removal of semiconductor structure remnants and/or polymer residueafter the removal of the binder matrix and embedded semiconductorstructures. That is, the remnants and/or residue may be left in place ifsubsequent fabrication steps do not require or are not impacted by thepresence of the remnants and/or residue. The absence of such a etchingor cleaning step may speed the preparation of the substrate forsubsequent semiconductor fabrication.

After the semiconductor structure remnants and polymer residue have beenremoved (if needed or desired), catalyst metal may be reapplied tofacilitate the growth of new semiconductor structures. Electrodepositionmay be used for the reapplication of the catalyst metal. To initiatereapplication of the catalyst metal, the substrate should be preparedfor electrodeposition. For example, if a Si wafer has been cleaned asdescribed above, it may then be placed with its oxide side down whilebuffered HF (aq) is applied to the back side of the wafer for 5 minutes.Application of the HF to the back side of the wafer provides for theremoval of any oxide from that side of the wafer. However, care must betaken to ensure that no HF contacts the oxide side of the wafer, sincethat may damage the patterned oxide layer.

After the substrate has been prepared for electrodeposition, electricalcontacts should be formed to facilitate the electrodeposition. After anyoxide has been removed from the back side of the Si wafer, the back sidemay be rinsed with 18 MS2 resistivity H₂O and dried under a stream of N₂gas. A piece of two-sided conductive Cu tape may then be applied to theback side of the wafer. This assembly can be made into an electrode byconnecting the other side of the Cu tape to a Cu wire in a glass tubeand using mounting wax to seal the tube and cover the wafer so that onlythe patterned oxide layer on the front is exposed. This electrode maythen be dipped in 10% (by volume) HF (aq) for 10 s to remove the nativeoxide at the bottom of patterned holes within the patterned oxide layeron the substrate and then rinsed thoroughly in water.

After the electrical contacts to support electrodeposition have beenformed and the substrate finally prepped for the application of catalystmetal, the electrodeposition may be started. After the Si waferelectrode has been formed and prepped as described above, the electrodemay then be immediately transferred to a catalyst metalelectrodeposition bath, such as an Au electrodeposition bath (forexample, Orotemp 24 from Technic Inc.). If Au metal is used, the Aumetal may be deposited into the patterned holes by setting a constantcurrent density of 0.4 to 0.8 mA cm⁻² of exposed wafer area between theSi working electrode and a Pt gauze counterelectrode and allowing it toproceed galvanostatically until 0.12 C cm⁻² of charge has passed. Ofcourse, alternative embodiments may deposit more or less Au, dependingupon the desired diameters of the Si wires to be grown. A PrincetonApplied Research Model 173 potentiostat may be used to make the chargemeasurement. The wafer with metal catalyst deposits in the patternedholes may then be removed from the electrode assembly by thoroughlydissolving the mounting wax in acetone. This should be done before thenext set of semiconductor structures are grown, as discussed below. FIG.4E shows a top-down SEM image of a reconditioned wafer afterelectrodeposition of an Au catalyst (the inset in FIG. 4E shows a 70°tilted image).

After the deposition of the catalyst metal, the second generationsemiconductor structures can be grown using the same technique as thatused for the first generation structures. Returning to the Si waferexample, the V-L-S technique described above and illustrated in FIGS.1A-1G can be used to form a second set of wire arrays, which can then beencapsulated and removed as described above. FIG. 4F shows a top-downSEM image of a reconditioned wafer after a new wire array has been grown(the inset in FIG. 4F shows a 70° tilted image). Subsequent polymercasting and peeling, patterned surface regeneration, metal catalystelectrodeposition, and wire regrowth stages may be repeated to fabricatea third and fourth generation (or more) of wire arrays on the same setof Si wafers. FIGS. 5A-5D show the successive wire array generationsobtained using the methods described above. FIG. 5A is a top-down SEMimage of the first generation of wire arrays (the scale bar is 40 μm).FIG. 5B is a top-down SEM image of the second generation (the scale baris 40 μm). FIG. 5C is a top-down SEM image of the third generation (thescale bar is 40 μm). FIG. 5D is a top-down SEM image of the fourthgeneration (the scale bar is 40 μm). Note that defect density increaseswith successive generations.

As indicated, fidelity of the oxide template pattern may break down, sothe substrate may be additionally prepared for reuse throughmechanically polishing or other techniques to remove the oxide layer andprepare the substrate for the application of a new patterned oxidelayer. For example, the Si wafers used to fabricate successivegenerations of wire arrays may be prepared to start the cycle again bysubjecting them to mechanical polishing followed by thermal oxidation. Awafer may be mounted with wax onto a polishing chuck, and its surfacewas smoothened by employing a South Bay Technology polishing wheel. Itcan be successively exposed to 1200 grit SiC paper, a 15 μm size aluminaparticle suspension, a 1 μm size alumina particle suspension, and a 0.3μm size alumina particle suspension. The polished Si wafer may then beput into a tube furnace under a fully hydrated atmosphere of industrialgrade air at 900° C. for 8 h, resulting in a surface oxide 300-400 nmthick. The Si wafer can then be photolithographically patterned to formthe desired array pattern (other patterning techniques may be used),covered in an evaporated catalyst layer, subjected to lift-off, and putin a reactor under the same process conditions (as described above andshown in FIGS. 1A-1G) that were used to grow the first generation of Siwires on a new wafer. This reconditioned Si wafer can then be used toform additional generations of wire arrays as described above. FIG. 6shows a tilted view SEM image of a Si wire array grown from a Si (111)wafer that has been mechanically polished and then thermally oxidized.The scale bar is 40 μm.

As indicated above, other methods may be used for the fabrication ofsemiconductor structures in accordance with embodiments of the presentinvention. For example, the semiconductor structures may be deposited ona substrate, rather than via a growth process. In such a case, transferand release of the deposited semiconductor structures would beaccomplished in much the same manner as described above. After thesemiconductor structures are formed, a binder material layer would bedeposited around the structures and the binder material layer with theembedded structures would be separated from the substrate. Still anothersemiconductor structure fabrication process using etching of thesubstrate would still provide the opportunity for substrate reuse. Afterthe semiconductor structures are formed in the substrate by etching awayportions of the substrate, a binder material layer would be depositedaround the structures and the binder material layer with the embeddedstructures would be separated from the substrate. Of course, in thiscase, the fabrication of the structures results in loss of material fromthe substrate, limiting the amount of substrate reuse.

Although it has been possible to fabricate Si wires of ideal dimensionsfor photovoltaics into vertically aligned, exceptionally uniform arrays,an expensive single crystal wafer substrate has been necessary to datefor each array in order to induce aligned, epitaxial growth. However, bytransferring the wires to a polymer matrix, reusing the patterned oxidefor several array growths, and finally polishing and reoxidation of thewafer surface to close the cycle, the cost of the substrate can beamortized across hundreds of wire arrays. Embodiments of the presentinvention may be employed with many different polymer materials, as wellas with any surface-initiated semiconductor structure growth method.

The foregoing Detailed Description of exemplary and preferredembodiments is presented for purposes of illustration and disclosure inaccordance with the requirements of the law. It is not intended to beexhaustive nor to limit the invention to the precise form or formsdescribed, but only to enable others skilled in the art to understandhow the invention may be suited for a particular use or implementation.The possibility of modifications and variations will be apparent topractitioners skilled in the art. No limitation is intended by thedescription of exemplary embodiments which may have included tolerances,feature dimensions, specific operating conditions, engineeringspecifications, or the like, and which may vary between implementationsor with changes to the state of the art, and no limitation should beimplied therefrom. This disclosure has been made with respect to thecurrent state of the art, but also contemplates advancements and thatadaptations in the future may take into consideration of thoseadvancements, namely in accordance with the then current state of theart. It is intended that the scope of the invention be defined by theClaims as written and equivalents as applicable. Reference to a claimelement in the singular is not intended to mean “one and only one”unless explicitly so stated. Moreover, no element, component, nor methodor process step in this disclosure is intended to be dedicated to thepublic regardless of whether the element, component, or step isexplicitly recited in the Claims. No claim element herein is to beconstrued under the provisions of 35 U.S.C. Sec. 112, sixth paragraph,unless the element is expressly recited using the phrase “means for . .. ” and no method or process step herein is to be construed under thoseprovisions unless the step, or steps, are expressly recited using thephrase “comprising step(s) for . . . ”

1. A method for fabricating semiconductor structures comprising thesteps of: (a) forming a templated oxide layer on a substrate, whereinthe templated oxide layer comprises openings in the oxide layer for theformation of semiconductor structures; (b) depositing a catalyst in theopenings in the oxide layer; (c) growing a set of semiconductorstructures on the substrate, wherein the semiconductor structure growthis supported by the catalyst deposited in the openings in the oxidelayer; (d) encapsulating the fabricated semiconductor structures in abinder material matrix; (e) releasing the fabricated semiconductorstructures from the substrate; and (f) reusing the substrate forfabricating additional semiconductor structures by etching and cleaningthe substrate and repeating steps (a) through (e).
 2. The methodaccording to claim 1, further comprising conditioning the substrateafter performing steps (a) through (e) and before performing step (f).3. The method according to claim 1, wherein encapsulating the fabricatedsemiconductor structures in a binder material matrix comprisesdepositing a film layer on a top surface of the templated oxide layer,wherein the film layer comprises the binder material matrix and whereinthe film layer conformably fills gaps between grown semiconductorstructures at and above the top surface of the oxide layer.
 4. Themethod according to claim 3, wherein releasing the fabricatedsemiconductor structures from the substrate comprises separating thefilm layer and the grown semiconductor structures from the oxide layerat or near a location where the film layer contacts a top surface of theoxide layer to provide a set of semiconductor structures embedded in thefilm layer.
 5. The method according to claim 1, wherein semiconductorstructures comprise vertically aligned wire arrays.
 6. The methodaccording to claim 1, wherein the binder material matrix comprises apolymer.
 7. The method according to claim 1, wherein the catalystcomprises gold, copper, nickel or some combination thereof.
 8. Themethod according to claim 2, wherein additionally conditioning thesubstrate comprises mechanically polishing the substrate.